What, When & Why to Aerate
Many home owners struggle with thin looking lawns and search for ways to thicken up their turf. Hard compact soil is typically a “root cause” for thin looking lawns and “lawn aeration”, “core aeration” or “aerification” is a great place to start for a lot of reasons.
What is core aeration
Core aeration is a mechanical process performed with a machine called a “core aerator.” This machine is taken across the lawn and in the process, it removes cores of soil that are about the size of your thumb. By doing this you accomplish 3 things:
- Removing the cores creates space (holes) that allow air, water and nutrients to penetrate deeper into the soil. This is especially true if you have very hard, compacted clay soil that doesn’t allow penetration easily.
- Removing the cores also creates space that can be filled up with grass roots but also you can sweep compost or other organic material across the lawn and into the holes which will, over time, change the composition of said soil.
- The process punches holes in thatch which can help to keep it in check.
Here is a video that shows you the basic operations of a core aerator.
Curing the process, the cores are deposited back on the lawn and should not be raked up. Leave them there and over the next few mowings, they will be broken down and spread/melted back into the lawn.
How much does core aeration cost?
Core aeration can be hired out to a professional, or you can do it yourself. I always tell people that doing your own core aeration is like a right of passage for the homeowner. “Enjoy the butt kicking” is what I tell folks. Running an aerator is not easy and the machine will beat you up, but it’s good for you!
You can expect to pay between $40 and $60 for a 4 hour rental of a core aerator. Most tool rental places, including Home Depot will have a few on hand but for sure call ahead because in the fall when most folks are aerating, they can be often “sold out.”
Keep in mind, if you are going to rent an aerator, you will need a pickup truck to haul it and they take 2 people to pick up, sometimes 3. An aerator can weigh 250 lbs for the smaller units and up to 400 or more for larger ones.
If you hire out your core aeration, you should be sure to check Facebook marketplace in late summer because there are young entrepreneurs who will actually rent aerators themselves (or buy one) and spend a week or two aerating lawns all over town for side money. If you find one of these guys, you can probably get your lawn aerated for around $50 if it’s around 5,000 sq ft.
If you hire one of the larger companies like TruGreen, that same 5,000 sq ft lawn would probably cost you in the neighborhood of $75 to be aerated and this is assuming they can even fit you into the schedule.
How often and when is the best time to core aerate?
If your lawn soil is highly compacted as clay soil across much of the US is, you can aerate every single year and the best time to core aerate your lawn is fall. Here’s why:
Lawns put in roots in the fall time and core aeration helps that.
In the fall time we are not concerned as much with annual weeds that the aeration may stir up seed from. Whereas in spring time, we apply pre-emergents to stop crabgrass and if you aerate after applying a pre-emergent, you will disrupt its effectiveness and crabgrass can sneak through. This is not a concern in fall.
Fall time is also the best time to seed the lawn and seeding works great right after an aeration because all that “opening up” of the lawn helps the seed stay in place as well.
Here is a full video where I talk you through the best time to aerate the lawn:
Core aeration and overseeding
One thing to mention here is that core aeration is primarily a process reserved for those with cool season lawns. Cool season grass types are Kentucky Bluegrass, Turf Type Tall Fesche and perennial ryegrass. These are “bunch type” grass and they benefit greatly from core aeration whereas the warm season grasses like Bermuda, St Augustine, Centipede and Zoysia are not really in as much need because they are creeping grasses that can spread and punch down with roots, even into the hardest soils.
But if you do have a cool season lawn, it is highly recommended that you throw down some grass seed right after you aerate your lawn. As mentioned above, the stirring up of the soil that the aerator creates is helpful in keeping your seed from washing away. Literally, seed will fall into the holes and grow but it will also grow in and around the entire lawn.
If you do plan to seed along with your aeration, you will want to “triple pass” with the machine and also apply “starter fertilizer” right on top. Here is a full video where I show you the process from start to finish:
What is liquid aeration?
In recent years, a different process known as “liquid aeration” has become popular. Liquid aeration isn’t a complete substitute for traditional mechanical core aeration, but does offer a viable alternative for folks who are not able to mechanically aerate their yards.
I’ve been doing this for a long time and I know for sure that 98% of DIYers don’t mechanically aerate their lawns. They are either scared of the process all together, don’t have the truck or trailer to get the aerator home, can’t afford the rental or just don’t believe the effort put in is worth the hassle. And you know what? There is nothing wrong with that. It’s best to just be honest with yourself and if you are not going to go to the trouble to core aerate your lawn, then liquid aeration is for sure the very best next option.
It also makes a great addition to those of you who will mechanically aerate your lawn because as I mentioned, liquid aeration for sure can accomplish “some” of the same things a mechanical aeration does.
Liquid aeration allows water penetration deeper into the soil and that is its primary function. Keep in mind, if water is penetrating your hard, compacted soil, it’s also dragging nutrients along with it and there for sure is air being exchanged.
What’s in liquid aerate / Air8 and how does it work?
Liquid aerations “Air8” from Greene County Fertilizer Co is a unique formulation that contains potassium hydroxide. Potassium hydroxide, when exposed to damp soil, chemically breaks bonds which creates microscopic fractures throughout making space and allowing water penetration.
Unique to Air8 is also the addition of humic acid that is essentially a carbon source that helps to fill those spaces created. Important to note is that you want to water the lawn prior to an application of liquid aeration Air8 and also water it in afterward. If you apply Air8 (or any liquid product) to a completely bone dry soil it will not penetrate. So be sure you water the day before your application and then water it after to get it to dive down and do its work in the soil.
How often to liquid aerate?
One of the advantages to liquid aeration is you can apply it any time of year. With mechanical aeration it’s very difficult to actually pull plugs in the lawn in the midst of summer when the clay is super compacted and dry. However, liquid aeration Air8 can be watered deep at any time of year. However, if you want to be logical, the best time to apply Air8 is spring and fall when your lawn is putting in most of its root growth. (again talking to cool season lawns mostly).
Additionally, liquid aeration Air8 will NOT interfere with your pre-emergent applications in spring and fall because it doesn’t disturb the barrier creed by these chemicals.
In general, 2 applications of liquid aeration Air8 are sufficient for most lawns. Spring and fall. However, if your lawn is severely compacted, then 2 applications in spring and 2 applications in fall are recommended.
Note: if you have a warm season lawn such as Bermuda, St Augustine, Zoysia or centipede, then liquid aeration Air8 will help with your compaction issues without disrupting stolon or rhizome growth making it the perfect choice for these grass types.
Where do I buy liquid aeration?
Core Aeration vs. Liquid Aeration
Many folks will ask if they should still mechanically aerate their lawns if they are using liquid aeration. The truth is, you can have a VERY healthy lawn without either one. On the flipside, you can have healthier soil with both, faster.
The real key to all of this is to get more organic materials and carbon introduced into your soil so that it supports healthy turf growth to a greater degree.
Mechanical aeration alone will not add any organic material or carbon to the soil unless you take my advice above and rake some compost in afterward. You can also use products such as XSOIL Soil Amendment Fertilizer applied after aeration to get them directly into the soil to improve it over time.
Liquid aeration Air8 can also help get carbon into your soil as it has it in the mix already in small amounts. Improving your soil with liquid aeration isn’t a stand alone prospect though - it’s recommended you apply humic acid all during the year along with and in addition to the Air8 to help this process. I also recommend you use fertilizers that contain natural or organic nutrients which also increase soil carbon over time. Milorganite is a great example here.
At the end of the day, here is what I recommend:
If you have a cool season lawn, you should plan to mechanically aerate this coming fall time. Do it just for the experience, but also for the benefit. After you aerate, cover the lawn with compost or peat moss to get it introduced deeper and start to change your soil’s composition. If you are a real savage Lawn Care Nut, spray down RGS and Air8 right after your mechanical aeration and also overseed and apply starter fertilizer. Then water like crazy to really thicken that lawn up!
If you are someone who will tell me straight up “I’m not going to all that trouble” then I recommend the next best thing which is to get the Compaction Cure Combo and spray that down twice in the fall time, water it in! This is the next best way to move ahead to a healthier soil without going to all the hassle of taking a beating from the mechanical aerator.